Arthrodesis or joint fusion is a well known procedure for osteosynthesis often associated with the spine, the ankle or the wrist. In particular, the wrist or carpus is the complex joint between the forearm and the hand. It allows the hand three degrees of movement important to manual dexterity: flexion/extension in the palmar-dorsal plane; adduction/abduction, also referred to as radial or ulnar deviation, in the medial-lateral plane and circumduction, the combination of both movements. These degrees of movement combine with the degrees of movement provided by the forearm (pronation/supination), the elbow (flexion/extension) and those of the shoulder to give the hand a vast positional range.
Wrist arthropathy occurs when the wrist joint becomes diseased as a result of trauma, osteoarthritis (OA) or rheumatoid arthritis (RA) among other causes. In wrist arthropathy, movement of the wrist causes severe pain that makes the patient hesitant to use the affected hand, thereby creating a substantial degree of disability. The pain in wrist arthropathy is the result of motion-exacerbated irritation of afferent nerves within the wrist bones resulting from inflammation or from bone-on-bone contact that follows degeneration of articular cartilage.
The treatment of wrist arthropathy centers upon balancing two contradictory objectives: relieving motion induced pain while attempting to retain as much motion as possible.
Medically, the most common treatment of arthropathy relies on the use of nonsteroidal anti-inflammatory drugs (NSAIDs) that relieve pain without affecting motion. Corticosteroids, sometimes combined with anesthetic, are also used to alleviate pain but the results are almost always transient. Conservatively, forced rest by applying removable external splints that temporarily limit motion is often useful but, if overused, can lead to subsequent stiffness or weakness from the immobilization.
Several surgical approaches have been developed to alleviate pain while attempting to preserve motion to the greatest degree possible. In some cases, partial denervation of the wrist can reduce pain and may allow postponement of more immobilizing procedures. Wrist arthroplasty (replacement) has evolved considerably in the last decades and may be a preferred procedure in some patients because it preserves a less painful, albeit decreased range of motion.
Wrist arthrodesis is performed to relieve intractable pain that cannot be relieved by conservative or medical treatment and, sometimes, after failed denervation or arthroplasty. Wrist arthrodesis is an established surgical technique to join (fuse) adjacent bones in the wrist by rigidly positioning them at their articular surfaces. By maintaining this placement, sometimes in the presence of bone graft, bone cell growth is stimulated, causing the bones to fuse together. Once the bones fuse, all motion that existed at the worn joint surfaces ceases and the pain caused by the irritation of the afferent nerves is significantly reduced or eradicated.
In limited or partial wrist arthrodesis a selected group of wrist bones are fused. Variations of the procedure such as triscaphe, radioscaphoid, radiolunate, scapholunatecapitate and four-corner fusion attempt to alleviate pain by fusing those articulations determined or suspected of originating pain and may be indicated, among others, in patients that require intricate use of their hands because more residual motion of the wrist can be preserved. The trade-off is that only rarely does the procedure result in full relief of pain.
Total wrist arthrodesis is very effective in relieving pain but all three wrist motions are permanently lost, thereby reducing manual dexterity. The trade-off, on the positive side, is that the elimination of pain permits the recovery of finger mobility and a relatively strong grip which, previously, would have been compromised by pain.
Fracture fixation is another form of osteosynthesis, involving the reduction and internal fixation of a bone fracture with an implantable device. In contrast to arthrodesis of a joint, discussed above, fracture fixation unites the ends of a fractured bone by mechanical means, such as a bone plate.